Any American MD can ask the FDA for "expanded access" to use a medication not approved by the FDA. 99% of the time the FDA grants expanded-access requests.

However, a recent review in NEJM explained how it is time consuming and expensive to apply for expanded-access and often the pharmaceutical companies refuse to distribute the drugs even after the FDA grants expanded-access.

http://www.nejm.org/doi/full/10.1056/NEJMhle1409465

"Compassionate use" is a separate, but related concept with different rules than "expanded access". And in the EU expanded access is often called "named-patient".